Large loop antenna



NOV. 8, 1966 BRYANT LARGE LOOP ANTENNA 2 Sheets-Sheet 1 Filed Jan. 15, 1964 Nov. 8, 1966 J. J. BRYANT 3,284,801

LARGE LOOP ANTENNA Filed' Jan. 15, 1964 2 Sheets-Sheet 2 FEICU'Z United States Patent 3,284,801 LARGE LOOP ANTENNA John J. Bryant, 359 Hawthorn Ave., Glen Ellyn, Ill. Filed Jan. 15, 1964, Ser. No. 337,821 Claims. (Cl. 343-743) This invention relates to directable radio antennas. More particularly, it is a system which provides a light, efiicient, high-gain antenna which can be directed and tuned while in operation by remote control.

It is well known that the large loop is highly eflicient as a radiator. The main reason why it is not more widely used is because its large size heretofore has required structures which tend to be cumbersome, complex and expensive as well as unstable.

One example of the large loop is the cubical quad which is used by many amateur radio licensees. It consists of wire loops mounted parallel coaxially, each being tensioned into a rectangular shape by means of diagonal beams which are supported at their junctures. The beams are inherently flexible. Since wind and ice loading on such a structure very often exceeds the dead weight, increasing the thickness of the beams greatly increases the live loading area on the antenna. For this reason the rotatable large loop antenna has proved uneconomical for frequencies below about 14 megacycles.

More compact types of rotatable antennas have been widely used. Some of them are designed for multi-band use. But they usually involve loading coils and capacitors and various other ineans, many of which are empirically designed and critically adjusted achieving flexibility and compactness while sacrificing efficiency. Most of these antennas have long elements which like the quad are unstable.

Accordingly, it is the object of this invention to provide an antenna which is highly efficient, low in cost, with excellent directive properties, light in weight, presenting minimum weather loading area, inherently a rigid form, which can be adapted to work equally well on several bands, and which can be tuned and rotated while in operation.

To meet the requirements I have made the radiator elements in the form of a ring which is sufiiciently rigid, light and thin to be supported upon a boom solely by means of thin tension members. The ring is constructed of straight sections of aluminum tubing plugged to keep out water and sprung into a circle. Insulating spokes in sufiicient number hold the ring in the circular shape which presents very little area to the weather. Unexpected advantages of this configuration become apparent upon reading the detailed description with the attached drawings wherein;

FIG. 1 is an isometric view of a two-element parasitic antenna adapted for horizontal rotation and use in two frequency bands. It is attached to a radio frequency current device such as a transmitter 32;

FIG. 2 is a front view of a driven element adapted for impedance matching to a balanced line;

FIG. 3 is a detail showing a method of connecting sections of tubing to form the ring member;

FIG. 4 is a detail of the spoke connections at the supporting boom;

3,284,801 Patented Nov. 8, I966 FIG. 5 is a detail illustrating a method of connecting an unbalanced feedline to the ring;

FIG. 6 is a detail of an alternate feed method providing an impedence matching means to the driven element of the loop antenna;

FIG. 7 shows a capacitive means for remote controlled tuning of the elements.

One model which was built in the manner illustrated FIG. 1 illustrates two light-weight structures generally designated as 1 and 2. The first contains the driven elements 3a, 3b. The second contains parasitic elements 4a, 4b. The rings 3a, 4a are made of straight sections 6, FIG. 3, of metallic tubing snugly plugged together with a shorter section of tubing 7 of different diameter. They are sprung into the curved shape of 3a thus providing good electrical contact at these points. Non-conducting radials 8a, 8b are needed to give only a tensile reaction on the ring. Thin twine of fiberglass or plastic is used for the radials. It insulates the ring and can be rolled on a spool when the antenna is disassembled.

The twine is connected at the ring 4a by means shown in FIG. 3. Two of the radials 8a, 8b consist of a single length of twine looped, in the middle. During manual adjustment of the antenna the distance between elements 1, 2 may require changing. A man on the ground can reach only the bottom segment of the element 2. However with two hands the ring can be turned inside out. Therefore the whole element 2 can be rolled within the loops of twine 8a, 8b causing the distance to change. The hub ends of the radials are attached as shown in FIG. 4 to an adjustable clamp 11. Formed integrally with the clamp 11 are T shaped clasps 10. The cable 8 is looped about the T as shown. The arms of the T are pinched around the cable to form a permanent connection. The clamp 11 can be turned on the boom or slid along, thereby taking up the slack in the radials 8. Screw 12 is tightened to fix the clamp 11 on the boom. It can be seen that by sliding clamps 11 or turning them on the boom 9 the tension and angle 13 of the radials 8 can be adjusted to space properly the elements 4a, 412 from their respective elements 3a, 3b. By turning the clamps in opposite directions, the cable is wound up on the boom without appreciably changing the angle 13 or the cables can be turned in the same direction for tuning as is described in a later paragraph. A standard rotator 14 provides the rotational means for boom 9 relative to mast 47.

FIG. 5 illustrates a means for connecting feedline 15a to the driven element 3a. To provide the proper impedance for the line 15a, insulating plug 16 is inserted between the sections 6 and screws 17 are provided for connecting the feedline 15a, and the strain relieving loop 18 to the antenna.

Where the impedance encountered is too low for the line, a gamma matching device will provide the necessary adjustment. FIG. 6 illustrates such a means. The line 15a is connected by means of screws 17 which are threaded into insulating block 21 which is slideably mounted over the ends of sections 6 of the element 3a. Screws 17 pinch the ends 6 and feed line 15a making electrical contact between the two. A metallic block 20 also is slideably mounted over ends 6 which are similarly pinched to cause conduction between screws 19. It can be seen that the circumference of the element as well as the impedance of the gamma match can be adjusted by sliding the blocks 20, 21 relative to the ends 6 of the element.

FIG. 2 illustrates another type of loop construction. Element 22 consists of a continuous rod or tube of spring metal or the like in which the ends are welded together at 23. This element is flexible enough to be looped as a band saw blade is looped for storage. Two of the radials 24 are metallic cables which form a delta match, general- 1y designated as 28. The ends of the cable are connected to the line 25, at insulating hub 26 by means of binding posts 27. The delta match is connected at the element 22 as shown. Since the loop 22 is always electrically symmetrical about the delta match only one cable requires adjustment. Conductor 24 is connected at the center of clamp 29. The loop 22 is slipped through holes in the sides of the clamp which, due to its resilience, binds the loop 22. The sides when squeezed togther allow the position of the clamp to be changed, thus changing the impedance of the delta match 28.

FIG. 1 shows secondary elements 3b, 4b. They can be wires attached to the radials and are tuneable to higher frequencies than that of the main loop. It has been demonstrated that the circular loops display reduced polarizing of the signal. This antenna is less discriminatory against the polarity of received signals and transmits one that can be more easily received by a distant station regardless of the polarity of its receiving antenna. The larger cross sectional area of the ring has much less ohmic resistance than does the wire of the quad. In close spaced antennas like this one, large conductors are necessary to realize the gain which is possible. The frequency range of this antenna is broad by virtue of the smaller length-to-diameter ratio of the tubing conductor.

FIG. 7 illustrates a method of changing the resonant frequency of the full wave loop. When used as a driven element, loop can be modified by attaching Wires 44 near each point of maximum voltage 30. It was found that the added capacitance of the wire could be increased by bending its ends away from the loop thereby lowering the resonant frequency of the loop. As in the goldleaf electroscope, the angle of the wires determines its charge or capacity.

Another effect was discovered where the wires were attached to the parasitic loop. When element 5 was a parasitic loop and the driven element contained maximum current moving in a horizontal direction, the maximum current was induced in the upper and lower segments of the parasitic element 5 and the maximum voltage 30 was in the vertical segments of element 5. With wires 44 mounted on the vertical segments of element 5, the position of the wires can be changed so that the added ca pacitance can be varied continuously from maximum to minimum merely by rotating the element 5 about the boom 9. A motorized hub 31 was clamped to the boom 9 and adapted to rotate the element through ninety degrees. It was found that the front-to-back rat-i0, standing wave ratio, gain and resonance could be varied by remote control of this motor while the antenna was energized.

In the foregoing description various features of the invention have been demonstrated as they are applicable to more familiar antenna circuits. It is to be understood that, due to present empiric methods of antenna circuit design, other adaptations of this invention will become apparent as it is further developed within the scope of the claims.

What is claimed is:

1. In a loop antenna comprising a slender, resilient wand wherein each portion thereof, tending to conform to a straight line, has substantially equal resistance to bending about any bending axis in a typical cross section thereof, means deflecting said wand substantially within the elastic limit thereof to form a non-self-sustaining loop; support means positioned substantially on the axis of said loop; thin flexible tensioned insulating members connected to said loop and extending in opposite directions from the plane of said loop to said support means for sustaining said loop; means for transferring radio frequency energy of substantially a resonent frequency in said loop to and from said loop and a radio frequency current device.

2. In a parasitic antenna including a driven element and a parasitic loop element as defined in claim 1 wherein said support means comprises a beam and said tensioned insulating members are connected at one end to said beam in front of said loop, wrapped about a segment of said loop and connected at the other end to said beam in back of said loop whereby torsion applied about any said segment causes all said segments to roll within said wrapping to vary the spacing between said elements.

3. In a loop antenna, the combination of a radiator comprising a slender, resilient wand wherein each portion thereof, tending to conform to a straight line, has substantially equal resistance to bending about all bending axes in a typical cross section thereof, said wand deflected into a loop within the elastic limits thereof; antenna support means on the axis of said loop, thin flexible insulating members connected to and tensioned between said loop and said support means for supporting and stabilizing said loop, means for feeding radio frequency energy of substantially a resonant frequency of said radiator to and from said loop, said last mentioned means comprising the ends of said wand being positioned to face in opposite directions and laterally spaced from each other, clamp means secured to said ends of said wand and adapted to make sliding electrical contact along said wand, said clamp means including an electrical connection for a radio frequency current device.

4. In a loop antenna, the combination of a radiator comprising a slender, resilient wand wherein each portion thereof, tending to conform to a straight line, has substantially equal resistance to bending about all bending axes in a typical cross section thereof, said wand deflected into a loop within the elastic limits thereof; antenna support means on the axis of said loop, thin flexible insulating members connected to and tensioned between said loop and said support means for supporting and stabilizing said loop, means for feeding radio frequency energy of substantially a resonant frequency of said radiator to and from said loop, said last mentioned means comprising an adjustable impedance transforming means comprising a pair of flexible conductors electrically connected to said loop and tensioned directly between said loop and said support means, one of said flexible conductors being connected to said loop by means of a clamp adapted to make sliding contact along said loop, terminal means on said support for connecting said flexible conductors to a radio frequency current device, and means mounting said loop for rotation about the axis of said loop.

5. In a loop antenna, the combination of a radiator comprising a slender, resilient wand wherein each portion thereof, tending to conform to a straight line, has substantially equal resistance to bending about all bending axes in a typical cross section thereof, said wand deflected into a loop within the elastic limits thereof; antenna support means on the axis of said loop, thin flexible insulating members connected to and tensioned between said loop and said support means for supporting and stabilizing said loop, means for feeding radio frequency energy of substantially a resonant frequency of said radiator to and from said loop, means mounting said loop for rotation about the axis of said loop, a conducting body attached References Cited by the Examiner UNITED STATES PATENTS Monti-Guarnieri 343-868 Aubert 343-807 Kandoian 343-742 Ramsay 343-741 Radclifi'e 343-868 Caraway 343-744 FOREIGN PATENTS 633,148 10/1927 France.

OTHER REFERENCES The A.R.R.L. Antenna Book, American Radio Relay League, 1956, pages 206-207.

HERMAN KARL SAALBACH, Primary Examiner.

10 ELI LIEBERMAN, Acting Examiner.

R. F. HUNT, Assistant Examiner. 

1. IN A LOOP ANTENNA COMPRISING A SLENDER, RESILIENT WAND WHEREIN EACH PORTION THEREOF, TENDING TO CONFORM TO A STRAIGHT LINE, HAS SUBSTANTIALLY EQUAL RESISTANCE TO BENDING ABOUT ANY BENDING AXIS IN A TYPICAL CROSS SECTION THEREOF, MEANS DEFLECTING SAID WAND SUBSTANTIALLY WITHIN THE ELASTIC LIMIT THEREOF TO FORM A NON-SELF-SUSTAINING LOOP; SUPPORT MEANS POSITIONED SUBSTANTIALLY ON THE AXIS OF SAID LOOP; THIN FLEXIBLE TENSIONED INSULATING MEMBERS CONNECTED TO SAID LOOP AND EXTENDING IN OPPOSITE DIRECTIONS FROM THE PLANE OF SAID LOOP TO SAID SUPPORT MEANS FOR SUBSTAINING SAID LOOP; MEANS FOR TRANSFERRING RADIO FREQUENCY ENERGY OF SUBSTANTIALLY A RESONENT FREQUENCY IN SAID LOOP TO AND FROM SAID LOOP A RADIO FREQUENCY CURRENT DEVICE. 